There is no ESS VT2 600 kit according to their website now. After the 585 kit it's the 625 kit. I ordered through a vendor right at the point ESS was doing a change to their kits. According to Roman it's slightly tweaked from the older 600 kit to still accept 91 octane. Probably minimal power difference. At the time of purchase I wasn't the one communicating with Roman - the vendor was.

In that case I'd put the emphasis on the vendor regarding communication. Not a big deal but with an SC kit I'd like to know all the details on my own kit.